The invention relates to a cleaning apparatus for a photosensitive member of an electrophotographic machine, and more particularly, to such apparatus in which a developing toner which remains attached to a photosensitive member carrying an electrostatic latent image is removed by utilizing a rotating cleaning brush.
As is well recognized, for an electrophotographic copying machine of the dry type which utilizes a developing toner in the form of powder, a cleaning apparatus is used to remove unnecessary developing toner which remains attached to a photosensitive member carrying an electrostatic latent image after a toner image has been transferred onto a record sheet. A variety of cleaning apparatus have been proposed in the prior art. However, such apparatus generally comprises a rotating cleaning brush disposed for contact with the photosensitive member, in combination with a toner trap associated with the brush for collecting the toner removed by the brush. The trap includes a filter which prevents the removed toner from dispersing into and outside the machine, and suction means.
A cleaning apparatus of such kind is associated with a striker rod disposed for abutment against the cleaning brush so that the toner attaching to the brush may be shaken off therefrom. The rod strikes the brush to remove the toner therefrom, and is provided because the efficiency to remove toner from the photosensitive member degrades and the dispersion of the toner tends to increase as the cleaning apparatus continues to be used over a prolonged period of time. However, it is found that as the striker rod becomes contaminated by the deposition of the toner, there occurs a phenomenon called a filming on the surface of the photosensitive member, resulting in a substantial degradation in the image quality achieved.
In the cleaning apparatus described above, the cleaning brush contacts the surface of the photosensitive member while rotating in order to remove any residual toner from such surface. However, the cleaning action does not remain perfect, but after a given period of use, a thin film of toner is formed on the surface of the photosensitive member to cause an adverse influence upon the copying operation. Such formation of a toner film is referred as a filming phenomenon. The purpose of the striker rod is to prevent the occurrence of such a filming phenomenon. However, experiments have shown that a strong adherence of the toner onto the surface of the rod or a local abrasion produced in the rod results in a decreased cleaning effect leading to the occurrence of a filming phenomenon.
It is also found by experiments that the striker rod may be temporarily rotated to change its surface adapted to engage the brush in order to avoid the above disadvantage. The number of revolutions of the rod may be as low as one revolution per one thousand copies.
An electrophotographic copying machine of the type described is usually designed to provide a multiple copy operation in which a single electrostatic latent image formed by one exposure is utilized to produce a plurality of copies. During a multiple copy operation, a toner developing step and a transfer step are repeated with a common latent image, and hence an exposure unit, a charger, a cleaning apparatus and a neutralizer lamp are left inoperative. Also the cleaning brush is arranged to be movable into contact with or away from the photosensitive member so that it may be left inoperative during such operation in order to avoid any degradation in the quality of the latent image. At this end, the rotatable brush is supported by a pair of rockable arms, so that the arms may be rocked to move the brush into contact with or away from the photosensitive member.